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Research Papers: Design Theory and Methodology

J. Mech. Des. 2019;141(9):091101-091101-12. doi:10.1115/1.4043316.

This paper investigates relationships among the cognitive characteristics, interaction behaviors, and ideation outcomes of 14 engineering design teams engaged in concept generation. Cognitive characteristics were measured using the Kirton Adaption-Innovation Inventory (KAI), which assesses an individual’s cognitive preference for structure in generating and working with ideas in problem solving. Team interactions were assessed using the Interaction Dynamics Notation (IDN), which allows interaction behaviors to be quantitatively analyzed, while team outcomes were measured in terms of ideation utterances (ideas and unique ideas). Our analyses revealed that cognitive style (KAI) did not correlate significantly with interaction response behaviors (IDN) or with the quantity of ideas/unique ideas produced. However, the cognitive style diversity of the teams did influence the number of topics they discussed, as well as the interconnectedness of those topics. In addition, several specific interaction responses were associated with the occurrence of ideas/unique ideas, although the sequences associated with those responses varied widely; the more adaptive teams also had greater position specificity in these sequences than the more innovative teams. Our findings highlight the importance of forming cognitively diverse design teams and suggest that specific interaction behaviors should be encouraged or taught as a means to increase the occurrence of ideas and/or unique ideas during team concept generation.

Topics: Design , Teams
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):091102-091102-10. doi:10.1115/1.4042793.

Customers post online reviews at any time. With the timestamp of online reviews, they can be regarded as a flow of information. With this characteristic, designers can capture the changes in customer feedback to help set up product improvement strategies. Here, we propose an approach for capturing changes in user expectation on product affordances based on the online reviews for two generations of products. First, the approach uses a rule-based natural language processing method to automatically identify and structure product affordances from review text. Then, inspired by the Kano model which classifies preferences of product attributes in five categories, conjoint analysis is used to quantitatively categorize the structured affordances. Finally, changes in user expectation can be found by applying the conjoint analysis on the online reviews posted for two successive generations of products. A case study based on the online reviews of Kindle e-readers downloaded from amazon.com shows that designers can use our proposed approach to evaluate their product improvement strategies for previous products and develop new product improvement strategies for future products.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):091103-091103-11. doi:10.1115/1.4042844.

Products evolve over time to satisfy new customer needs, technologies, and markets. The evolution process of products necessarily involves changes in a product structure that might be characterized by inherent evolving properties. Although product evolution has been discussed from various perspectives, the underlying properties of an evolving product structure have not been sufficiently explored from an analytical view. Various empirical and theoretical studies in network science show that real networks representing different types of complex systems are not randomly structured but are characterized by certain properties regardless of their origins. Focusing on the topological universality of real networks, this study aims to reveal the inherent evolving properties of a product structure based on a network science approach through a case study of generational smartphone models. First, the product structure of each generational product is represented as a product structure network. Then, topological characteristics and patterns in each network are analyzed by network measures and motifs. The results show that the product structure networks may follow the universal properties observed in other real networks; the product structure grows as a scale-free network with common building blocks. The findings from this study suggest that the identified properties can be used as a basis to understand and formulate product evolution to obtain design benefits from topological robustness and modularity.

Commentary by Dr. Valentin Fuster

Research Papers: Design Automation

J. Mech. Des. 2019;141(9):091401-091401-9. doi:10.1115/1.4043201.

In engineering design problems, performance functions evaluate the quality of designs. Among the designs, some of them are classified as good designs if responses from performance functions satisfy a target point or range. An infinite set of good designs in the design space is defined as a solution space of the design problem. In practice, since the performance functions are analytical models or black-box simulations which are computationally expensive, it is difficult to obtain a complete solution space. In this paper, a method that finds a finite set of good designs, which is included in a solution space, is proposed. The method formulates the problem as optimization problems and utilizes gray wolf optimizer (GWO) in the way of design exploration. Target points of the exploration process are defined by clustering intermediate solutions for every iteration. The method is tested with a simple two-dimensional problem and an automotive vehicle design problem to validate and check the quality of solution points.

Topics: Design , Optimization
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):091402-091402-8. doi:10.1115/1.4042791.

Origami has provided various interesting applications in science and engineering. Appropriate representations and evaluation on crease patterns play an important role in developing an innovative origami structure with desired characteristics. However, this is generally a challenge encountered by scientists and engineers who introduce origami into various fields. As most practical origami structures contain repeated unit cells, graph products provide a suitable choice for the formation of crease patterns. Here, we will employ undirected and directed graph products as a tool for the representation of crease patterns and their corresponding truss frameworks of origami structures. Given that an origami crease pattern can be considered to be a set of directionless crease lines that satisfy the foldability condition, we demonstrate that the pattern can be exactly expressed by a specific graph product of independent graphs. It turns out that this integrated geometric-graph-theoretic method can be effectively implemented in the formation of different crease patterns and provide suitable numbering of nodes and elements. Furthermore, the presented method is useful for constructing the involved matrices and models of origami structures and thus enhances configuration processing for geometric, kinematic, or mechanical analysis on origami structures.

Commentary by Dr. Valentin Fuster

Research Papers: Design of Mechanisms and Robotic Systems

J. Mech. Des. 2019;141(9):092301-092301-9. doi:10.1115/1.4042625.

This paper presents a transformation method to generate the workspace of an n(3RRS) serial–parallel manipulator (S–PM). Firstly, the boundary of the workspace of the 3RRS parallel manipulator (PM) is obtained using the boundary search method and verified by MATLAB/SimMechanics simulation. Secondly, the workspace of the 2(3RRS) S–PM is obtained using the proposed method and verified by MATLAB/SimMechanics simulation. Finally, the workspace of the 3(3RRS) S–PM is obtained using the proposed method. The results indicate that the n(3RRS) S–PM can significantly expand its workspace with the increase in the number of PMs connected in series, and the proposed method can generate the workspaces of n(3RRS) S–PMs efficiently with the advantages of simple operation, high efficiency, and high accuracy. The proposed method is applicable to all S–PMs that are composed of PMs, and it provides a reference for solving the workspaces of other types of redundantly hybrid manipulators.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):092302-092302-9. doi:10.1115/1.4042792.

This research proposes the self-similarity design concept of flexible mechanisms by studying the out-of-plane, piston motion of a compliant device. Self-similar compliant mechanisms can be formed by connecting flexible units of scaled-down, identical geometry in series and/or parallel. We study a folded-architecture, compact mechanism class formed of multiple flexible, circular, and concentric segments that are serially connected. The device is capable of producing large displacements by summing the small deformations of its units. A simple analytical model is derived, which predicts the mechanism piston compliance/stiffness in terms of configuration, geometry, and material parameters. Experimental testing of a prototype and finite element simulation of various designs confirm the validity of the mathematical model. Several particular designs resulting from the generic architecture are further characterized based on the analytical model to highlight the mechanism stiffness performance and the way it scales with its defining parameters and unit stiffness.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):092303-092303-12. doi:10.1115/1.4042845.

A new method is presented for the design of kinematotropic linkages based on 2-DOF kinematic chains that generate more than one surface. As an example of the proposed method, a kinematotropic linkage is obtained by studying a special case of the Bohemian dome which has two different parametrizations constructed by translation of circles and, therefore, two different hybrid kinematic chains can be designed to generate the same Bohemian dome. Each of these hybrid kinematic chains can generate two different surfaces and, thus, can be used in the proposed method. Parametrizations for the secondary surfaces are then obtained and studied. A total of 27 motion branches are found in the configuration space of this kinematotropic linkage. The singularities in the configuration space are further determined using the properties of the surfaces. The resultant linkage offers an explanation of Wholhart’s queer-square linkage other than its original paper folding. As part of the analysis of this example, the relationship between the properties of self-intersections in generated surfaces and the configuration space of the generator linkage is studied for the first time, leading to a description of motion branches related to self-intersections of generated surfaces.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):092304-092304-9. doi:10.1115/1.4043019.

The operation effectiveness of multi-bar transplanting mechanisms is low, and the specific changing law of the transmission ratio (the curve of the transmission ratio has twice unequal amplitude [TUA] fluctuation.), which is needed in vegetable pot seedling transplanting, is difficult to fulfill using a planetary gear train with noncircular gears and a single-planet carrier. To address this problem, we propose a noncircular gear pair that comprises an incomplete noncircular gear, rack, partial noncircular gear, and elliptical gear. The structural characteristics and the working principle of the TUA gear pair were analyzed. The pitch curve equation of the noncircular TUA gears was derived from the relationship of the angular displacement of the corresponding pitch curves. The influence of central angle α and eccentricity k on the shape of the pitch curve, angular displacement, and transmission ratio of the TUA gear pair was analyzed. The TUA gear pair was applied to a proposed vegetable seedling pickup mechanism (SPM) considering the design requirements. Finally, the feasibility of the new noncircular TUA gear transmission mechanism was verified by an SPM test.

Topics: Gears
Commentary by Dr. Valentin Fuster

Research Papers: Design of Direct Contact Systems

J. Mech. Des. 2019;141(9):093301-093301-14. doi:10.1115/1.4042846.

This paper presents a novel design approach to systematically synthesize available configurations for dedicated hybrid transmission (DHT) systems subject to design constraints and required operation modes by using simple planetary gear sets (PGSs). The configuration synthesis process includes two main steps. The first step is the synthesis of the PGSs by synthesizing all the components to a simple PGS subject to the design constraints. The second step is to combine the structural and shift elements into all configurations and detect those meeting the requirements with the mechanical and operation mode constraints. By applying the proposed design approach, the configurations of the Toyota’s hybrid systems (THSs) and Voltec-II prove the feasibility of the method. Furthermore, several new DHT configurations are synthesized under the new design conditions. The proposed design approach is capable of systematically synthesizing new DHT systems with multiple PGSs, variable design constraints, and expected modes.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2019;141(9):093302-093302-12. doi:10.1115/1.4043206.

A new active ease-off topography modification approach is proposed to improve the meshing performance of hypoid gears based on a fourth-order predesigned transmission error (PTE) model and a modified error sensitivity analysis method. Ease-off topography modifications that describe local deviations of pinion tooth surfaces can be conducted by converting the fourth-order PTE into equivalent deviations of pinion tooth surfaces. The modified error sensitivity analysis method is developed to investigate the effects of misalignments on the moving velocity of a contact point of a hypoid gear pair. The moving velocity of the contact point can describe transmission error (TE) curve shapes of ease-off tooth surfaces. The ease-off topography modification approach can achieve TE precontrol and modification curvature adjustment of the pinion for stable meshing performance of the hypoid gear pair. Moreover, pinion ease-off tooth surfaces are finished by a five-axis computer numerical control swarf-cutting machine tool. Swarf-cutting tests and TE measurement tests are conducted on hypoid gear pair specimens to demonstrate the feasibility and effectiveness of the proposed methodology.

Commentary by Dr. Valentin Fuster

Technical Brief

J. Mech. Des. 2019;141(9):094501-094501-5. doi:10.1115/1.4042619.

This paper aims at dealing with the deployment vibration problem of the rigid-links deployable mechanism caused by mobility bifurcation. A triangular prismoid deployable mechanism with mobility bifurcation is employed as an example to demonstrate the design and analysis process. First, the mobility of the triangular prismoid deployable mechanism is analyzed, which shows that there exists mobility bifurcation and the possibility of deployment vibration. Second, the revolute joints that introduce mobility bifurcation are analyzed, which shows that they can be replaced by the elastic joints without changing its mobility. Third, a detailed design procedure for this type of elastic joints is discussed; the main parameters of the elastic joints can then be determined based on the mobility and motion range of the deployable mechanism. Physical prototypes of both the rigid-links prismoid deployable mechanism and the corresponding improved mechanism with elastic joints are fabricated, and the deployment experiments of both mechanisms are conducted to show improvement in the latter mechanism.

Commentary by Dr. Valentin Fuster

Design Innovation Paper

J. Mech. Des. 2019;141(9):095001-095001-9. doi:10.1115/1.4043313.

This study introduces a new potential energy-based design method for simplifying elastic gear bodies in low- to mid-range frequency applications by bridging over the gear teeth with external stiffness elements. The advantage of the introduced method over more traditional approaches, which are either based on rigid gears or on replacing the teeth, is that the complex gear body and its dynamic behavior are preserved, albeit with fewer degrees of freedom. The method is demonstrated on a gear by replacing a single tooth under load and then validated numerically against a typical flexible gear model. The simulation results show good accuracy within the chosen frequency range and with a clear reduction in calculation time compared to the unreduced model. Furthermore, the extension and optimization potential of the results is discussed.

Topics: Stress , Gears , Stiffness , Modeling
Commentary by Dr. Valentin Fuster

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